This invention relates to a process for producing optically active 4-amino-2-methylbutane-1-ol useful as an intermediate for synthesizing optically active medicines and pesticides, a salt of optically active 4-amino-2-methylbutane-1-ol with an optically active organic acid, a process for producing the salt, a process for producing optically active 4-amino-2-methylbutane-1-ol by using the salt, a process for using the optically active 4-amino-2-methylbutane-1-ol obtained by the above-mentioned process as an intermediate for synthesizing optically active medicines and pesticides, and a process for producing optically active medicines and pesticides by using the optically active 4-amino-2-methylbutane-1-ol obtained by the above-mentioned process.
With regard to a process for producing optically active 4-amino-2-methylbutane-1-ol, there have been reported a process for synthesizing the compound by reducing optically active 2-methyl-4-aminobutyric acid with lithium aluminum hydride (J. Am. chem. Soc., 81, 4946-4951 (1959)) and a process for synthesizing the compound by reducing a methyl ester of optically active 2-methyl-4-nitrobutyric acid with lithium aluminum hydride (J. Plant Growth Regul. 2 (1), 47-57 (1983))
However, the former process has a disadvantage of low yield; in the latter process, the safety of nitromethane used as a starting material and the yield of its addition reaction are low, hence it is difficult to use such processes as an industrial production process.
On the other hand, as to a process for producing racemic 4-amino-2-methylbutane-1-ol, it can be prepared, for example, by obtaining methyl-3-cyanoisobutyrate from hydrocyanic acid and methyl methacrylate, and then reducing the product with an alkali metal hydride in a suitable solvent according to a process described in JP-A-8-291157. However, no report has been made about an optical resolution of racemic 4-amino-2-methylbutane-1-ol as in the present invention.
With regard to a formation of a diastereomeric salt of an optically active organic acid (optically active reagent for optical resolution) with a low molecular weight amino-alcohol, there are known a salt of optically active mandelic acid with optically active 2-amino-1-butanol (US 4260815A, US 4259521A, and EP 518B1) and a salt of said optically active mandelic acid with optically active 2-benzylamino-1-butanol (US 4239912A). However, these amino-alcohols referred to in these documents are restricted only to xcex2-amino-alcohols in which an amino group is directly bonded to asymmetric carbon and it has been utterly unknown whether or not these disclosures can be applied to 4-amino-2-methylbutane-1-ol of this invention, that is, a compound in which the amino group is not directly bonded to asymmetric carbon, or not.
The object of this invention is to provide an industrially advantageous process for producing optically active 4-amino-2-methylbutane-1-ol useful as an intermediate for synthesizing optically active medicines and pesticides.
The other objects of this invention are to provide a process for producing, industrially advantageously, optically active 4-amino-2-methylbutane-1-ol from a diastereomeric salt of optically active 4-amino-2-methylbutane-1-ol with an optically active reagent for optical resolution and a process for recovering, industrially advantageously, an optically active reagent for optical resolution from a diastereomeric salt of optically active 4-amino-2-methylbutane-1-ol with the optically active reagent for optical resolution.
The present inventors have made extensive study to achieve the above-mentioned objects. As a result, it has been found that optically active 4-amino-2-methylbutane-1-ol can be obtained by reacting, preferably in the presence of a solvent, an optically active organic acid on racemic 4-amino-2-methylbutane-1-ol and then separating thus obtained diastereomeric salt from a mother liquor. This invention was accomplished on the basis of the above finding.
Further, the present inventors have made extensive study to attain the above-mentioned objects. As a result, it has been found that when a diastereomeric salt of optically active 4-amino-2-methylbutane-1-ol with an optically active reagent for optical resolution is contacted with a solvent and an alkali to decompose the salt and the reaction mixture is subjected to solid-liquid separating, optically active 4-amino-2-methylbutane-1-ol can be obtained from a filtrate with a high purity and high yield, and further that the reagent for optical resolution used can be recovered by contacting a filtration residue containing an alkali salt of the reagent for optical resolution obtained by the solid-liquid separation with a solvent and an acid and then subjecting the reagent for optical resolution thus crystallized out to solid-liquid separation. This invention was accomplished on the basis of the above finding.
Further, the present inventors have found that when a salt of optically active 4-amino-2-methylbutane-1ol with an optically active reagent for optical resolution is contacted with a solvent, e.g. an alcohol and water etc., and an alkali, e.g. an alkali metal alcoholate and alkali metal hydroxide etc., to decompose the salt, and the solvent, e.g. an alcohol and water etc., is replaced with an alcohol in which a solubility of an alkali salt (alkali metal salt) of the optically active reagent for optical resolution is low, and an alkali salt (alkali metal salt) of the optically active reagent for optical resolution and a solution of optically active 4-amino-2-methylbutane-1-ol are subjected to solid-liquid separation, the alkali salt (alkali metal salt) of the optically active reagent for optical resolution can be recovered and optically active 4-amino-2-methylbutane-1-ol can be obtained. This invention was accomplished on the basis of the above finding.
Thus, this invention relates to a process for producing optically active 4-amino-2-methylbutane-1-ol which comprises reacting an optically active organic acid on racemic 4-amino-2-methylbutane-1-ol, crystallizing out the resulting diastereomeric salt and subjecting the diastereomeric salt to solid-liquid separation.
Further, this invention relates to a salt of optically active 4-amino-2-methylbutane-1-ol with an optically active organic acid.
Further, this invention relates to a process for producing the above-mentioned salt and to a process for producing optically active 4-amino-2-methylbutane-1-ol by using the salt.
Further, this invention relates to a process for producing optically active 4-amino-2-methylbutane-1-ol which comprises contacting a diastereomeric salt of optically active 4-amino-2-methylbutane-1-ol and an optically active reagent for optical resolution with a solvent and an alkali to decompose the salt, followed by solid-liquid separation to obtain a filtrate, and obtaining optically active 4-amino-2-methylbutane-1-ol from the filtrate.
Further, this invention relates to a process for producing optically active 4-amino-2-methylbutane-1-ol which comprises contacting a filtration residue containing an alkali salt of the optically active reagent for optical resolution obtained by solid-liquid separation in the above-mentioned process with a solvent and an acid, and recovering the thus crystallized optically active reagent for optical resolution by solid-liquid separation.
Further, this invention relates to a process for producing optically active 4-amino-2-methylbutane-1-ol which comprises contacting a diastereomeric salt of optically active 4-amino-2-methylbutane-1-ol and an optically active reagent for optical resolution with a solvent and an alkali to decompose the salt, replacing the solvent with an alcohol in which a solubility of an alkali salt of an optically active reagent for optical resolution is low, and subjecting the alkali salt of the optically active reagent for optical resolution and an optically active 4-amino-2-methylbutane-1-ol solution to solid-liquid separation to recover the alkali salt of the optically active reagent for optical resolution.
Further, this invention relates to a process for producing optically active 4-amino-2-methylbutane-1-ol which comprises contacting a diastereomeric salt of optically active 4-amino-2-methylbutane-1-ol and an optically active reagent for optical resolution with an alcohol and an alkali metal alcoholate to decompose the salt, replacing the alcohol with an alcohol in which a solubility of an alkali metal salt of an optically active reagent for optical resolution is low, and subjecting the alkali metal salt of the optically active reagent for optical resolution and an optically active 4-amino-2-methylbutane-1-ol solution to solid-liquid separation to recover the alkali metal salt of the optically active reagent for optical resolution.
Further, this invention relates to a process for producing optically active 4-amino-2-methylbutane-1-ol which comprises contacting a diastereomeric salt of optically active 4-amino-2-methylbutane-1-ol and an optically active reagent for optical resolution with water and/or an alcohol and an alkali metal hydroxide to decompose the salt, replacing the water and/or alcohol with an alcohol in which a solubility of an alkali metal salt of an optically active reagent for optical resolution is low, and subjecting the alkali metal salt of the optically active reagent for optical resolution and an optically active 4-amino-2-methylbutane-1-ol solution to solid-liquid separation to recover the alkali metal salt of the optically active reagent for optical resolution.
Further, this invention relates to a process for recovering the optically active reagent for optical resolution used in the production of optically active 4-amino-2-methylbutane-1-ol and to a process for producing optically active 4-amino-2-methylbutane-1-ol by reusing the optically active reagent for optical resolution recovered by the recovering process.
Further, this invention relates to a process for using the optically active 4-amino-2-methylbutane-1-ol obtained by the above-mentioned production process as an intermediate for synthesizing optically active medicines and pesticides and to a process for producing optically active medicines or pesticides by using the optically active 4-amino-2-methylbutane-1-ol obtained by the above-mentioned production process.